The invention relates to an anti-skid device for motor vehicles with a plurality of resilient spreading arms distributed over the circumference of a support which can be pressed against the tire of a vehicle and can be set into a revolving motion, to which chain strands forming the anti-skid means are attached, of which the ends remote from the spreading arms are thrown away from the support by the effect of centrifugal force when the support revolves in the service position, and of which at least parts pass through the region of the ground contact surface of the tire when the vehicle tire rotates.
An anti-skid device of the above-mentioned type is known from German Offenlegungsschrift No. 2,914,366, in which the spreading arms are constructed as cable sections or chain strand sections firmly enclosed by rubber envelopes. The rubber envelopes in this case exhibit at one end a head provided with an annular groove, which serves conjointly with a closing ring to anchor the spreading arms to the support, and the resilient properties of which should permit an easy exchange of the spreading arms and of the chain strand retained by them. The known solution cannot be satisfactory, if only because here the strength of the anchorage of the spreading arm and of the chain strand connected to them on the support is inadequate. Apart from this fact, the vulcanization process which is unavoidable in the case of the known construction represents an unfavorable burden on the production costs of the spreading arms.
The object of the spreading arms is to transfer the chain strands, which form the anti-skid means, into a favorable position relative to the tire rolling surface and/or to the wedge gap between vehicle tires and road. Any entangling of the chain strands should also be counter-acted. The same purpose is served in an anti-skid device known from U.S. Pat. No. 3,068,949 by traction springs interposed between the anti-skid elements and the support, one end of each of which exhibits an eye for a screwbolt serving for fastening the springs to the support. In the case of this second known device the traction springs, due to the fact that they have to transmit powerful centrifugal forces, must exhibit substantial torsion cross-sections, which impose narrow limits to their flexibility. Furthermore, substantial cyclic forces occur in the transition region between the fastening eye and the main part of the spring; these involve the danger of premature fatigue fractures.
Lastly, French Pat. No. 409,260 discloses an anti-skid device in which chain strands forming anti-skid means are connected by springs to a support. However, in this device the support is not adapted to be pressed against the vehicle tire, and the springs serving to drive it are likewise exposed to not inconsiderable traction forces.